Saturday, June 22, 2013

Serial MRI Helps Manage Iron Overload (CME/CE)

By Chris Kaiser, Cardiology Editor, MedPage Today Reviewed by Robert Jasmer, MD; Associate Clinical Professor of Medicine, University of California, San FranciscoA series of MRI exams over time is central to early identification and treatment of cardiac iron overload in patients with beta-thalassemia major, according to a consensus statement from the American Heart Association.Point out that iron cardiomyopathy can be reversed with iron removal treatments, and patients should be treated in, or transferred to specialty centers where physicians are skilled in handling heart failure in beta-thalessemia major.

A series of MRI exams over time is central to early identification and treatment of cardiac iron overload in patients with beta-thalassemia major, according to a consensus statement from the American Heart Association.

Beta-thalassemia major (TM) is a genetic condition that is particularly life-threatening in a child's first few years. Life-long blood transfusions are required, as is iron chelation treatment to prevent or reverse iron overload, according to the statement, published online in Circulation: Journal of the American Heart Association.

The use of cardiac MRI, although more expensive then echocardiography but also radiation-free, is considered the gold standard for the measurement of all left and right ventricular (LV, RV) indices, wrote Dudley J. Pennell, MD, of the National Heart and Lung Institute of Imperial College in London, and colleagues.

It accurately assesses LV volumes and function, and is more reproducible than other techniques in serial imaging.

"Therefore, it is preferred for follow-up of patients over time when it is available," researchers said.

The use of late gadolinium enhancement in cardiac MR allows for the identification of myocardial replacement fibrosis, which can be useful in the diagnosis of myocarditis and myocardial infarction, two "uncommon differential diagnoses in heart failure in TM patients," they wrote.

Heart failure is the most common cause of death in thalassemia and is mostly the result of iron accumulation. The use of chelation therapies have helped patients survive longer, but, ultimately, iron overload is still a dominant player in the cause of death.

In the past, about half of patients were expected to die within 1 year of heart failure onset. Now, with continuous chelation therapies, about two-thirds of patients are expected to survive beyond 5 years.

The iron chelators noted in the consensus statement include deferoxamine, deferiprone, and deferasirox. They each have different properties that affect how they should be administered.

Serum ferritin and liver iron concentration are not adequate surrogates for cardiac iron measurement.

Cardiac MR studies using a T2* sequence can show very heavy iron deposits in tissue. This allows for early intervention before the onset of symptomatic heart failure, Pennell and colleagues noted.

In fact, the authors pointed out, recent improvements in life expectancy of thalassemia patients in the U.K. have been associated with the "increasing availability of T2* cardiac MR and earlier escalation of therapy."

CT imaging is a fast technique to assess heart function and can deliver data on liver iron concentrations, but the price for repeated studies is a considerable amount of exposure to ionized radiation.

In addition, the use of beta-blockers to slow the heart rate for CT imaging "can affect the functional analysis," according to the consensus statement.

Exercise stress testing is not recommended as exercise capability correlates with the degree of anemia and is not considered useful to diagnose preclinical disease.

Symptoms of heart failure that are specific to TM patients include liver congestion as manifest through abdominal or back pain and nausea and usually associated with reduced ventricular function and raised B-type natriuretic peptide (BNP). Other symptoms include dizziness or presyncope, and the inability to tolerate standard transfusions. Two later symptoms are peripheral edema and orthopnea.

The authors noted that classic heart failure signs may appear late, potentially delaying diagnosis and "appropriate intensification of chelation."

Importantly, iron cardiomyopathy can be reversed with iron removal treatments, and patients should be treated in, or transferred to specialty centers where physicians are skilled in handling heart failure in TM.

Pennell reported relationships with AMAG, Apotext, NIHF, Novartis, Siemens, Shire and CVIS. Relationships of the co-authors include ApoPharma, Novartis, and Ferrokin Biosciences.

From the American Heart Association:

Chris Kaiser

Cardiology Editor

Chris has written and edited for medical publications for more than 15 years. As the news editor for a United Business Media journal, he was awarded Best News Section. He has a B.A. from La Salle University and an M.A. from Villanova University. Chris is based outside of Philadelphia and is also involved with the theater as a writer, director, and occasional actor.

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